Electrical Discharge Machining (EDM), is a thermal-machining process that strips a workpiece of its material by electrolytic erosion and rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage.
Dielectric fluid in EDM fills the gap between the tool electrode and the workpiece to control electrical discharges during the material-removal process. It removes the debris particles, absorbs heat and cools the workpiece down.
Dielectric fluids, also known as insulating fluids, are commonly used in various power system equipment including transformers, tap changers, bushings, reactors, capacitors, and switching elements.
The Role of Dielectric Fluid
The role of dielectric fluid/oil acts as a capacitor that stores energy. Dielectric oil is used as an insulator and cooling agent to enhance the performance of high-permittivity dielectric materials.
In other words, dielectric fluid is essential to EDM as it cools down the process which in turn, enhances and supports the performance of molecule polarisation under electrostatic fields.
Dielectric Fluid is needed for dielectric materials such as glass, mica, plastic, oxides from various metals and porcelain.
Dielectric fluid also plays an integral role in determining high material removal rates (MRR) and surface finish during operations.
Types of Commonly Used Dielectric Fluids
Dielectric fluids play a crucial role in the process of electrical discharge machining (EDM) by acting as a medium for the sparks to travel between the electrode and the workpiece. There are several types of dielectric fluids commonly used in EDM, each with its own set of properties and advantages. In this section, we will explore some of the most commonly used dielectric fluids in EDM and discuss their characteristics and applications.
Hydrocarbon Oil
A synthetic solution designed to have high thermal conductivity, excellent dielectric properties, and compatibility with different materials in electronic systems.
Transformer Oil
Dielectric transformer oil functions as an insulator and cooler to a transformer’s metal components. It also prevents oxidation and corrosion around the core and windings of a transformer.
Paraffin Oil
Paraffin is a type of hydrocarbon oil commonly used as a fuel for jet engines and rockets, as well as a fuel or fuel component for diesel and tractor engines. Paraffin oil has a high viscosity index which is good for engine oil but bad for transformers.
Kerosene
Kerosene is a specific type of paraffin oil also used as a dielectric fluid. It is a great insulator that is used as a cheaper alternative to clear out the debris during the erosion process in EDM.
Dielectric Gas (Sulphur Hexafluoride)
Also known as an insulating gas or sulphur hexafluoride, dielectric gas is a material in a gaseous state that prevents electrical discharge. Although this is not a liquid, it is another popular dielectric material often used in power equipment and gas-insulated transmission lines.
Lubricating Oil
This broad term is used for dielectric oils designed to insulate, repel moisture, and prevent corrosion.
Advantages & Disadvantages of Using Dielectric Fluid in the EDM Process:
Advantages:
- Controls electrical discharge
- Stores energy
- Cools down the heated surfaces of the electrodes
- Increases number of entities used in EDM
- Quality dielectric fluids have high thermal stability and are not flammable.
Disadvantages:
- Low moisture saturation
Selecting the Right Dielectric Fluid
When selecting the right dielectric fluid for your workpiece/process, it’s important to consider several factors such as the stability and chemical properties of the fluid. Poor insulating fluid used in high-voltage systems can cause the failure of equipment and extensive areas without energy. If these events take place, large financial losses may occur.
You must also consider the following:
- Material compatibility
- Safety
- Viscosity
- Surface finish requirements
- Erosion resistance
- Longevity
- Cost
- Environmental impact
Dielectric Fluid In EDM Frequently Asked Questions
How long does dielectric fluid last?
Synthetic: Longer life, better performance, and excellent operator acceptance. Quality synthetic fluid can last up to 6 times longer than petroleum fluids.
Petroleum: petroleum fluid life span is usually less than a synthetic but it is a cheaper alternative to synthetic dielectric liquid.
Is dielectric fluid conductive?
What are the different types of EDM?
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To see how A&M could support your next complex manufacturing project – simply call us, or use the form below.